During welding of a joint formed between two surfaces, a backing plate may be used on one side of the joint when a large gap may be present in the joint or when there is a large variation in the joint. In such a situation, the backing plate may be permanently installed behind the joint after the welding, thus, adding extra weight and material cost to the joint. Also, the welded joint may have a lower fatigue class because of presence of stress risers in the joint leading to premature joint failure.
In some situations, the joint may be present in a confined area such that there may be limited or restricted access to set up the backing plate. In such a situation, a full penetration weld may have to be performed only from one side. As a result, a required quality of the weld joint may not be achieved. Further, a weld puddle formed during the welding may flow from sides of the joint and may get deposited therein after the welding as an excess material that could be a discontinuity or a defect. This excess material may lead to wastage of the material. Additionally, the excess material may have to be machined after the welding to complete the joint. This machining may add to welding time, effort and cost.
U.S. Pat. No. 2,792,490 describes a method of welding adjacent edges of two metal parts by the use of a welding torch and without the use of a backup plate. The method includes providing a consumable insert piece against which the edges of the parts to be welded together are abutted. The method includes moving the welding torch along one side of the insert and supplying sufficient heat through the torch to completely melt the insert to form successive molten weld puddles. The consumable insert is proportioned as to shape and composition such that the heat input from the welding torch completely melts the consumable insert and the parent metal of the parts being welded together.